U.S. Pat. No. 2,637,747 discloses the reaction of trichloroethylene and HF over an antimony pentachloride catalyst to obtain a 32% yield of HCFC-133a, no HFC-134a, and some 1,2-dichloro-1,1-difluoroethylene.
U.S. Pat. No. 2,744,147 discloses an alumina catalyst, which may be promoted with a metal (cobalt, nickel, and chromium), and a process using the catalyst in a fluidized bed for fluorinating haloalkanes at a temperature between 180.degree. to 425.degree. C. CF.sub.3 CH.sub.2 C1 (HCFC-133a) is positively excluded from the list of halocarbons taught to be fluorinated by the invention process (Col. 1, lines 43-53, 54-65).
U.S. Pat. No. 2,744,148 discloses an alumina catalyst which may be promoted with a metal (chromium, cobalt, nickel, copper, and palladium) and a process for fluorinating haloalkanes to highly fluorinated products. A process is disclosed which activates the catalyst and converts at least part of the alumina to basic aluminum fluorides. CF.sub.3 CH.sub.2 Cl (HCFC-133a) is again positively excluded from the list of halocarbons taught to be fluorinated by the invention process (Col. 2, lines 23-33, 34-46). U.S. Pat. No. 2,885,427 claims a process for forming a 1,1,1-trifluoro-2-haloethane by the reaction of HF and trichloroethylene over a basic chromium fluoride catalyst. Example 1 shows that this reaction affords the following products with the selectivities shown; HCFC-133a (94.2%), HFC-134a (3.6%), 1,2-dichloro-1-fluoroethylene (2.0%), and pentafluoroethane (0.2%); the conversion of trichloroethylene is 92.3%.
U.S. Pat. No. 3,003,003 claims a process for the manufacture of HCFC-133a by reacting trichloroethylene and HF over an antimony fluorochloride catalyst. In Example 2 a 67% yield of HCFC-133a is reported for this reaction.
GB 1,000,485 claims a process for the preparation of fluorinated organic compounds by passing a halo-olefin and HF over a catalyst consisting essentially of activated alumina which is partially fluorinated. The alumina catalyst may also contain polyvalent metals chosen from chromium, cobalt, nickel, and manganese. The patent discloses that the use of AlF.sub.3 as a catalyst is not always satisfactory partly because it "leads to several reaction by-products which may be present in large quantities" (page 2, lines 20-24). In Example 1, trichloroethylene is reacted with HF over a fluorinated alumina containing chromium and cobalt to yield HCFC-133a with a 94.1% selectivity, fluorinated olefins with a 2.7% selectivity and no HFC-134a.
U.S. Pat. No. 3,752,850 discloses a process for the manufacture of HCFC-133a by reacting trichloroethylene and HF in the presence of a catalyst, the composition of which can vary between CrF.sub.1.5 O.sub.1.5 and CrF.sub.2 O, or a catalyst, the composition of which can vary between CrFO.sub.2 and CrF.sub.2 O. In Example 8 it is shown that the process of the invention affords HCFC-133a in 94.8% yield and no HCFC-134a.
U.S. Pat. No. 4,129,603 discloses a process for the manufacture of HFC-134a which comprises reacting in the vapor phase at elevated temperature a haloethane of formula CX.sub.3 CH.sub.2 Y, wherein X is Br, Cl, or F and Y is Cl, with HF in the presence of a catalyst which is chromium oxide or which is at least in part basic chromium fluoride and wherein the HFC-134a product containing 1-chloro-2,2-difluoroethylene, which is an impurity, is removed by intimate contact with a metal permanganate in a liquid medium.
U.S. Pat. No. 4,158,675 discloses a process for the manufacture of HFC-134a which comprises reacting in the vapor phase at elevated temperature (300.degree. to 400.degree. C.) a haloethane of formula CX.sub.3 CH.sub.2 Y, wherein X is Br, Cl, or F and Y is C1, with HF in the presence of a catalyst which is chromium oxide or which is at least in part basic chromium fluoride and wherein the HFC-134a product stream containing 1-chloro-2,2-difluoroethylene, which is an impurity, and HF is brought into contact over said catalyst at a temperature in the range of 100.degree. to 275.degree. C.
U.S. Pat. No. 4,258,225 discloses the reaction of trichloroethylene and HF over a TaF.sub.5 catalyst to yield a mixture containing 1,2-dichloro-1,1-difluoroethane (41%), 1,1,2-trichloro-1-fluoroethane (57%) , and 1,1,1,2-tetrachloroethane (2%).
GB 2,030,981 claims a process for the preparation of HFC-134a which comprises reacting HCFC-133a with HF in molar excess at a temperature not lower than 300.degree. C. in the presence of an inorganic chromium (III) compound with the introduction of 0.002 to 0.05 mol O.sub.2 per mol of HCFC-133a into the reaction system. The patent also states that in this process, if the oxygen content is below the lower limit, catalyst deterioration occurs. When the oxygen content is more than the upper limit, catalyst deterioration is not a problem but the selective conversion to HFC-134a decreases. It is believed that this decrease in selectivity occurs because the catalyst promotes the oxidation of hydrogen chloride to molecular chlorine and water. [See Chemical Week, page 18, Jun. 24, 1987 for the use of chromium based catalysts for the oxidation of hydrochloric acid to chlorine and water]. The highest yield of HFC-134a reported is 29%.
JP 55-27138 claims a process for the preparation of HFC-134a by the reaction of HCFC-133a and HF in the presence of an inorganic chromium (III) compound. The highest yield of HFC-134a reported is 35%.
U.S. Pat. No. 4,792,643 discloses a process for the manufacture of HFC-134a by the reaction of CX.sub.2 .dbd.CHX, in which X is chlorine or bromine or a combination of both, with HF in the vapor phase at about 300.degree. C. to about 500.degree. C. over a catalyst prepared by codepositing hexavalent chromium oxide and a compound of a transition metal selected from the group consisting of titanium, zirconium, vanadium, molybdenum, and manganese on alumina, which is then contacted with HF, to form a product mixture from which HFC-134a is recovered. In one example 68% of trichloroethylene is converted to products with the following selectivities: 20% HFC-134a, 50% HCFC-133a and 30% other products, which include CClF.dbd.CHCl (FC-1121), CCl.sub.2 .dbd.CHF (FC-1121a), CF.sub.3 CHClF (HCFC-124), CHF.sub.2 CClF.sub.2 (HCFC-124a) and CF.sub.3 CH.sub.3 (HFC-143a). It is disclosed that HCFC-133a is available for further reaction either by extending the catalyst contact time, raising the temperature, or recycling.
The catalyzed reaction of HF with trichloroethylene to afford HFC-134a is a sequential reaction. The intermediate, HCFC-133a, can be produced in essentially quantitative yield; however the conversion in the second reaction of HCFC-133a with HF to yield final product, HFC-134a, is dependent on the HF/HCFC-133a ratio, the higher the ratio, the more HFC-134a is produced at a given temperature. In general, HCFC-133a is isolated as an intermediate and fed to a second reactor where the conversion to HFC-134a is conducted. A need exists for the manufacture of HFC-134a from trichloroethylene and HF without simultaneously producing significant amounts of deleterious by-products or the requirement of two reactors, one for making HCFC-133a and one for making HFC-134a from HCFC-133a, which increases the cost of manufacture. This is particularly true in view of the growing demand for commercial quantities of HFC-134a as an environmentally desirable refrigerant. The herein described invention affords HFC-134a from the reaction of trichloroethylene and HF with very little (less than 5%) by-products in a single reaction zone.